[PATCH] drm: Add drm.edid_quirk_param module parameter

[Keith Packard <keithp@keithp.com>]

This parameter allows the set of EDID quirks to be changed at
runtime. The syntax is

	vendor/product/quirks,vendor/product/quirks,...

where vendor is the three-letter EDID vendor value, product is the
EDID product id which may be prefixed with 0x to for hex instead of
decimal values and quirks is the replacement quirks value from the
list in drm_edid.c.

Signed-off-by: Keith Packard <keithp@keithp.com>
---
 drivers/gpu/drm/drm_edid.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 5dc742b27ca0..63b4587faddd 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -98,6 +98,12 @@ struct detailed_mode_closure {
 #define LEVEL_GTF2	2
 #define LEVEL_CVT	3
 
+#define EDID_QUIRK_PARAM_LEN	256
+static char edid_quirk_param[EDID_QUIRK_PARAM_LEN];
+module_param_string(edid_quirk_param, edid_quirk_param, sizeof(edid_quirk_param), 0644);
+MODULE_PARM_DESC(edid_quirk_param, "Extra EDID quirks, "
+		 "format is 'vendor/product/quirks;...' ");
+
 static const struct edid_quirk {
 	char vendor[4];
 	int product_id;
@@ -1774,8 +1780,24 @@ static bool edid_vendor(const struct edid *edid, const char *vendor)
 static u32 edid_get_quirks(const struct edid *edid)
 {
 	const struct edid_quirk *quirk;
+	const char *q;
 	int i;
 
+	for (q = edid_quirk_param; q && *q; q = strchr(q, ',')) {
+		char 	vendor[4];
+		int	product_id;
+		int	quirks;
+
+		while (*q == ',')
+			q++;
+
+		if (sscanf(q, "%3s/%i/%i", vendor, &product_id, &quirks) == 3) {
+			if (edid_vendor(edid, vendor) &&
+			    (EDID_PRODUCT_ID(edid) == product_id))
+				return quirks;
+		}
+	}
+
 	for (i = 0; i < ARRAY_SIZE(edid_quirk_list); i++) {
 		quirk = &edid_quirk_list[i];
 
-- 
2.18.0

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